Fig. 6.

Expression domains of abdominal Hox genes in larvae of the earliest holometabolans, the beetle Tribolium castaneum, and other modern taxa. The expression of Ubx, Abd-A and Abd-B Hox genes in larvae of the earliest holometabolans are shown at (a, b). The most closely related model species affiliated with the earliest holometabolans probably is the beetle Tribolium castaneum, whose pattern of Hox gene development is shown in the wild-type at (c), and an Ubx/Abd-A mutant in (d). A sample of the Hox gene effects on abdominal leglet development are given in (e–g), showing the variety of expression patterns on abdominal appendages in taxa of the Hymenoptera, Diptera and Lepidoptera. The expression domains of Distalless (Dll), and the Hox genes Ultrabithorax (Ubx), Abdominal-A (Abd-A) and Abdominal-B (Abd-B) [15] in holometabolous larvae is shown at (h). The colors represent, from anterior to posterior: orange, antennae; green, mouthparts; blue, thoracic legs; red, abdominal leglets; and yellow, cerci. The stemmata likely are present and the cerci are inferred in Srokalarva berthei